Just because client-side rendering did not work well for Twitter for a variety of reasons, does not mean it is subpar to server-side rendering in all cases. Performance-wise, if server_json_generate + json_download + client_render_json_to_html < server_html_generate + html_download + client_render_html, you can certainly go with client-side rendering.

In Twitter's case, client-side rendering was slow while server-side wasn't. In LinkedIn's case, html_download was slow while client_render_json_to_html wasn't. Performance aside, there are numerable reasons to go either away, all of which vary from project to project.

Having Worked with CoffeeScript + Twitter Bootstrap + BackboneJS/Underscore + LessCSS for some time now, I know I will not willingly go back to the old server-side ways unless there is a major reason to. Working fully client-side to make UI and relying on REST API / JSON is wonderful experience, especially when the app feels so responsive.

What about SEO? I've noticed a lot of these sites that are rendered client-side start with very little content in the HTML, doesn't this mean the search engines can't read the content?

According to this other LinkIn blog post, http://engineering.linkedin.com/frontend/leaving-jsps-dust-m... (look for SEO in the comments), they detect cases where the client can't or won't do JS and perform the rendering server-side.

How do they do that? I can't really figure out anything apart checking user agent (for web crawlers?)

you can simply check for the accepts header.

Can we assume that degradability isn't a concern for you? Accessibility?

Degradability is not a concern. Accessibility is, and client-side rendering does not mean no accessibility.

I'm a bit bemused that for me, I can't think of an area where LinkedIn is anything more than a straight HTML site. That is, why would they need something like this?

Why would they need a template engine? Erm.. because they have more than one user....

I mean to say that there doesn't seem to be any apparent use of node on LI. Is there a chat facility or something?